Ion-electron converters (IEC) have long been used for detecting ion currents and for investigating the mechanism of ion-induced secondary electron (SE) emission. For the detection of ion currents the ions involved are accelerated onto a solid surface capable of SE emission, i.e., the conversion electrode, and the current of the secondary electrons emitted on ion impact is measured with the aid of an electron detector (ED), e.g. a semiconductor surface barrier detector or a scintillation detector. With ion acceleration voltages of 20 kV and more and oblique ion incidence it is possible to attain high SE emission coefficients, to the effect that ion currents as low as 10.sup.-22 A can be measured with the IEC. Ion-electron converters and their applications are described e.g. in
Rev.Sci.Instr. 31 (1960) 264 PA1 Rev.Sci.Instr. 42 (1971) 1353 PA1 Int.J.Mass Spectrom.Ion Phys. 11 (1973) 255.
The known IEC, however, are generally not capable of complete collection of the secondary electrons, and, in addition, emission of field electrons due to the high electric field strength causes high background noise signals.